If your published code is bad I can quickly learn whether I'm wasting my time, but if it's good I still need to see you code in person. Neither GitHub nor homework proves you did the work.
>If your published code is bad I can quickly learn whether I'm wasting my time
Sounds good to me. I think we run the risk of training people not to publish, but that's why I like the author's advice to highlight one particular repo that is a showcase for how the individual works.